Spirobarbituric acids



Patented July 24, 1951 UNITED STATES PATENT OFFICE SPIROBARBITURIC ACIDS Wilbur J. Doran and Earle M. Van Heyniugen, Indianapolis, Ind., assignors to Eli Lilly and Company, Indianapolis, Ind., a corporation of Indiana No Drawing. Application March 19, 1949, Serial No. 82,484

in which R is a member of the group consisting of hydrogen and methyl, and R1 and R2 are members of the group consisting of methyl and ethyl; and R is hydrogen when both R1 and R2 are ethyl; and R is methyl when both R1 and R2 are methyl; and in which X representshydrogen when'the compound is an acid, and represents a metallic salt-forming radical when the compound is a salt. For pharmaceutical use, a solublesalt is preferred, for example, the sodium salt in which case X in the formula represents sodiumnx In their acid form; the new compounds have a relatively low water-solubility. Although the acid form is suitable for oral administration, for parenteral administration a water-soluble material is desirable and hence it is preferable to employ the compounds in the form of their water-soluble salts.

The new acids can be prepared by condensing a 1,1edicarbethoxycyclopentane with urea or guanidine. When guanidine is used, the iminobarbituric acid obtained is converted to the barbituric acid by hydrolysis. The salts can be prepared from the corresponding acids by reacting the acid with a suitable base, for example in the case of the potassium salt, by reacting the acid with potassium alcoholate in anhydrous alcohol solution or with potassium hydroxide in aqueous solution. Evaporation of the solution of the salt yields the dry salt.

; One method of preparing the acid compounds 7 Claims. (Cl. 260-257) The new compounds 2 of our invention is by the reaction indicated by the following equations, in which R, R1 and R2 have the same significance as hereinbefore, and E represents an esterifying radical, for example 5 a lower alkyl radical.

This is a continuation-in-part of application Serial No. 29,957, filed May 28, 1948, now abandoned This invention is further illustrated by the following specific examples.

EXAMPLE '1 Spiro(2,3,5 trimethylcyclopentane-1,5'-barbituric acid) is prepared by the following sequence of reactions:

B-methylacetonlyacetone (Yountz and Perkins, 1929, J. A. C. S. 51, 3514), dissolved in absolute ethanol, is reduced with hydrogen under pressure in the presence of Raney nickel catalyst. The reaction mixture is filtered, and the filtrate is distilled. The fraction boiling at 83-90 C. at a pressure of about 1.0 mm. of mercury is recovered and consists essentially of 3-methyl-2,5- hexanediol. This is cooled and saturated with dry hydrogen bromide gas and allowed to stand overnight. It is then resaturated with hydrogen bromide gas and warmed at 50-60 C. for about 7 hours. The mixture is then extracted, first with an equal volume of 48 percent hydrobromic acid solution and then with water, and then is of the sodium derivative of ethylmalonate), To the cool mixture, l.g:.of 3-meth'yl-;2,5'-dibromo+ hexane are added rapidly and the mixture is stirred for about an hour without heating. The

mixture is then heated and refluxed for about 2 hours, and then distilled to remove the alcohol.

Water is then added, which dissolves the sodiumbromide formed in the reaction, and forms a sep, The aqueous layeris separatedfrom.

arate layer. the Oily organic layer and extracted twice with benzene, and the benzene extracts are added, to the organic layer. 7 ture is dried with magnesium sulfate and distilled. The fraction boiling at 84-108 C. at a pressure of about 3 mm. of mercury is recovered,

and iconsists: essentially of ther 1,1 dicarbethoxy 2,3,,5Etrimethylcyclopentane;

Ara-mixtureis-prepared containing 4.2- g.;of-sodiumedissolved in .65. cc. of. absolute alcohol, 1 and' 8.2 g. of guanidine carbonate;-and to :this mixturel there are added 155 g. of l,1-dicarbethoxy-2,3,5- trimethylcyclopenta'ne. The resulting mixture is refluxed for 6 hours and is then distilled to remove the alcohol. The residueis cooled, water is added to it, and the aqueousmix-ture is extracted with ether to remove any alkali insoluble oil. The ether extract is discarded. Carbon dioxide, conveniently in dry solid form, is. added to the aqueous solution; which causes the precipitation of the desired spiro[2,3,5-trimethylcyclopentane-l,5'-(2'-imino)-barbituric acid], and this is recovered by filtration.

To a mixture of 2.5 cc. of concentrated hydrochloric acid and 7.5 cc. of water, 0.35 g. of spiro- [2,3,5-trimethylcyclopentane- 1,5 2-imino) -barbituric acid]. is-added, with heating to cause it to" go into solution. The mixture is refluxed for about two hours, and then cooled, which produces a precipitate in crude form of the desired spiro(2,3,5-trimethylcyclopentane-1,5'- barbituric acid) represented by the 'followifn'g iormuar Theprecipitate, is. recovered filtration, washed with water, and crystallized three timesfrom dilute. alcohol.

The combined organic mix- 4 11. The mixture is filtered, the filtrate is evaporated to dryness, and the residue thoroughly dried under vacuum at about 80 C. for several hours. The dry material is the desired sodium salt of spiro(2,3,5-trimethylcyclopentane-1,5- barbituric acid), which is represented by the following formula CH: CH;

. I EXAMPLE 3 'Spiro(2 ethyl-3,5-dimethylcyclopentane- 1,5-

barbituricacid) is prepared as follows:

Spiro 23,5-.trimethylcyclopentane 1,5'- barbie turi'cv acid l thus. prepared melted at about. 2169- 2l'7- 'C; Analysisshowed the presence. of about 12.25. percent nitrogen as compared with the calculated amount 'of. 12.50 percent nitrogen...

EXAMPLE 2 400,g.-of a-allyldiethyl ketone (Cope, Hoyle, and Heyl, 1941; J. A..C'. S. 63, 1850) are added to a mixture of 375g. of aluminum isopropoxide and 20001cc;of-isopropanol. The mixture is subjected towslow distillation througha fractionating column for about 11 hours. Most of the remaining'isopropanol is then distilled ofi, and the residue is cooled and acidified with dilute sulfuric acid while maintaining; the temperature below 40C} The mixture now-forms=two=layersrwhich" are separated. The oily layer is washedwitlr water and-dried; as-with magnesium sulfate;; and is then" distilled; The fraction boiling at 92 l00f* C; at a pressure of;;58 60'" mm: of ;-mercury- :is:r covered; and consists essentially-of4- methyll heptene-fi -ol.

This is convertedto 4-methyl=2;5= dibromohep tane; as: follows: To 390g; of4methyl-l-liep tene-5-ol are added-50' cc: of-glacial aceticaci'df 3 g. of diphenyl amine, and 20700. of water. The mixture is saturatedwith dry-hydrogen bromide gas, with cooling- ,7 and; then allowed to stand overnight. It is then resaturated with dry hydrogen bromide gas," with cooling, and then heated at 50-60 C. for about 2 hours. Upon standing, the mixture forms two layers, which are separated; and-the =waters'slayer-rissdiscardedii The other layer is; washed; with =waterziandiwithi sodium bicarbonate solution, and them dried with anhydrous potassium :carbonate: The dried: Zmaaterial'is filtered, and.-'fractional1y distilled: The: I

fraction; boiling..- at :907-1009 at: as pressure 10ft. 3"6- mm. of'zmercury is ;recovered; andi. conslstsessentially of4 methyl-2,5edibromoheptanee To a solution*of. '50"g; of sodium ,int750xcczt of'absolute alcohol; 3'46 g: of," ethyl '-.malonate:- are added, and the mixture cooled. andzstirredzi. To this mixture, 294, g. of 4-methyl-2,5- dibromor' heptane -are added, and the -resulting1mixture.= is stirred} forabout 2 hours; without external iheata ing. The mixture "is 'thenheatedfi andrrefluxedis. with continued'stirringr for aboutfi hours: and; isth'en: distilled to remove'the'alcohol'. Water; is added to the residuetodissolve sodiumbromide'r' formed in the reaction. The aqueous solution forms a separate layer :.which is'separatedmnd extracted with ether. The ether extractis added: to the oily layer,: and the organic mixture 'is dried with magnesium sulfate-and fractionally distilled. The material boiling at 138P'--139.".C; at a pressure of aboutflmm; of mercurycisrecoveredand consists-essentially of 1;1'-dicarbethoxy.- 2-ethyl-'3,5 dimethylcyclopentane;

Tea-solution of 5.4g." of sodium incc'.-ofi" absolute alcohol are i added 6.35 'g.: of guanidine carbonate and 12.6 g; of L'l dicarbethoxy 2eethyl- 3,5-dimethycyclopentane,'and the mixture. SIIIB*= distilled oil, and the residue cooled and dissolved in water. The aqueous solution is ex tracted twice with benzene and then filtered. The filtrate is neutralized with dilute acetic acid, which causes a precipitate of spiro[2-ethyl-3,5-

dimethylcyclopentane-1,5-(2'-imino) barbituric The precipitate is recovered, as by filtration, washed'with water, and crystallized four times from dilute alcohol.

-The purified crystalline acid thus prepared melted at about 186-187 C. Analysis showed thepresence of about 11.93 percent nitrogen as compared with the calculated value of 11.76 percent nitrogen.

. EXAMPLE 4 Preparation of the sodium salt of spiro(Z-ethyl 3,5 dimethyloyclopentane 1,5 barbituric acid) r A suspension of spiro 2 ethyl 3,5 dimethylcyclopentane-l,5-barbituric acid) in alcohol is treated with an amount of a solution of sodium ethylate in alcohol to bring the mixture to about pH 11. The mixture is then filtered, the filtrate evaporated to remove the alcohol, and the residue dried under vacuum at about 80 C. for several hours. The dry material is the desired sodium salt of spiro(2-ethyl-3,5-dimethylcyclopentane-1,5'-barbituric acid) which is represented by the following formula CH3 Na EXAMPLE 5 Preparation of spiro(2,3-dimethyZ-S-ethylmclopemtane-l ,5 bdrbiturio acid) with aluminum isopropoxide to form thecorresponding alcohol, treatment with hydrogen bromide to form 2,5'-dibromo-3-methylheptane, conversion of the dibromide into the cyclopentane-1,1-dicarboxylic ester, and condensation ofthe ester with urea to form the barbituric acid.

The barbituricacid is converted to its metallic salts by the procedure described in Examples 2 and 4. r 1

EXAMPLE 6 Preparation of spiro(2,5--diethylcyclopentdne 1,5-barbituric acid) Spiro(2,5 diethylcyclopentane-1,5'-barbituric acid) is prepared by the following sequence of reactions:

Acetylene dimagnesium bromide is prepared by passing acetylene into 3 mols of ethylmagnesium .bromide in 1500 cc. of ether until the reaction is complete. The mixture is allowed to stand for several hours and to it are added dropwise and with stirring 3 mols (174g) of propionaldehyde. After the addition is complete the reaction mixture is stirred for about one half hour at room temperature and is then poured into a mixture of dilute sulfuric acid and ice water. 4octyne- 3,6-diol separates as a, supernatant oily layer. The oily layer is separated and the aqueous layer is extracted four times with ether to recover the 4-octyne-3,6-dio1 dissolved therein. The ether extracts are added to the 4-octyne-3,6-dio1 and the mixture is washed with sodium carbonate: solution and dried with magnesium sulfate. The ether is removed by evaporation and the residue comprising 4-octyne-3,6-dio1 is purified by dis tillation in vacuo. The 4-octyne-3,6-diol boils at -95 C. at a pressure of about 1.0 mm. of mere cury.

41 g. of 4-octyne-3,6-diol are dissolved in 200 cc. of percent ethanol and 0.5 g. of platinum oxide catalyst are added. The mixture is hydrogenated with hydrogen at about 60 pounds pressure in an Adams machine until the calculated amount of hydrogen is adsorbed. The reaction mixture containing octane-3,6-diol is filtered to remove the catalyst, the alcohol is removed by disti1lation, and the residue comprising octane-3,6-diol is purified by distillation. Octane-3,6-diol boils at 101-102 C. at a pressure of about 3 mm. of mercury.

62 g. of octane-3,6-d1'0l are dissolved in a mixture of 70 cc. of ether and 5 cc. of glacial acetic acid. The reaction mixture is refluxed and dry.

hydrogen bromide gas is passed into the refluxing mixture for about eight hours, during which time most of the ether evaporates from the mixture. The reaction mixture is allowed to stand at room temperature for about 12 hours and the aqueous layer which forms below the organic layer is separated and discarded. The organic layer is heated to about C. and treated with dry hydrogen bromide gas for about 8 hours. tion mixture is allowed to stand for about 10 hours during which time a further quantity of aqueous layer appears below the organic layer. The aqueous layer is separated and the organic layer is Washed successively with water and sodium bicarbonate solution, and treated with anhydrous potassium carbonate. The organic liquid comprising 3,6-dibromooctane is purified by distillation. 3,6-dibromooctane boils at about 6370 C. at a pressure of about 1 mm. of mercury.

lute ethanol and to the solution are addedlll) g'.

The reac of'iethyl malonater Themixture isz-cooled=-and to-- th'ecool'mixture areraddedwBZfi g1; of 3,6'-.dibr0mo-.- octanei'andltheimixtureisstirred and refluxed for about hours. The ethanol is distilled from: the- Iriixture and theresiduei treated with :water and 1 the aqueous layer? containing: dissolved sodium.

diumin-10ccof absolute-ethanoh 6.3g. of urea are added and the mixture is refluxed for: about 81hours. The'ethanol is removed by distillation and? the residue :which contains spiro 2,5-diethyl-. cyclopentaneelfiZ-barbituric.acid). as its sodium salt is -dissolved .in water. The aqueous solution.

is acidified with. dilute hydrochloric acid'to precipitatethe. barbiturie. acid. The spiro(2,5-diethylcyclopentane-l,5'-barbituric acid) is filtered oft-washed with water and purified by repeated recrystallization from dilute ethanol. is represented by the following formula om- Hi (Jo-NH;

/V UHF-c e0 -N:

Spiro'( 2,5 diethylcyclopentane-l ,5 -barbituric acid) thus prepared melted at about l92-194 C. Analysis showed the presence of about 1158 percent nitrogen as compared with the calculated value of 11.76 percent nitrogen.

EXAMPLE-7 The sodium salt of spiro(2,5-diethylcyclopen tane LF-barbituric acid) is. obtained by the pro.- cedure describedfin Examples 2 and. 4. The sodium' salt is represented'by the formula EXAMPLE 8= Preparation of Spiro(2-mcthylJ-ethylcycZopentane-'1,5-barbituric acid) Spiro.( 2 methyl-5eethylcyclopentane- 1,5 -bar bituric. acid) is prepared by the following sequence. of reactions:

Sodium amide isprepared by reacting-138 g. of-ifmetallic so,dium.with 6 liters of liquid ammonia." To the mixture areadded slowly 246 g..

of. acetonitrileand the. mixture is stirred for 10 minutes. To. the vigorously. stirred mixture are added asrapidly as possible..726 g. of allyl .bromide. The. ammonia is=evaporated1 and to the solid residue are added 1500 cc. of Water and the mixture is. filtered. The filtrate which comprises an organic layer containing allylacetonitrileis separated from the aqueouslayer and the aqueous layer. is extracted. several times with ether. to recover the allylacetonitriledissolved therein. The ether extractsare added to the already separated allylacetonitrile, the mixture is dried .withanhydrous magnesium sulfate and the ether evaporated. The residue comprising allyl- The acid of absolute di-isopropyl ether. 'The mixture' ist refluxed r or about 2 hoursiand allowed .to'standl at room temperature forzaboutdhours; The reacw tion mixtureisrpourediinto.asmixtureof dilute hyedrochloric' acid and ice, and the ethereal; layers: which separates is recovered. Thezaqueous layer; is extracted several 1timesWitlr'benzenevandxthe: extracts added'to. the. ethereal .solution originally: recovered. The 'solution whichicontainsel hepetene-5-one is drieduovermagnesium' sulfatezand the solvent evaporated. The residual 1-heptene- 5-one is purified by distillation. It boils at about 142 C.

104 g. of l-heptene-E-on'e dissolved in 350 cc. of anhydrous isopropanol are treated with 110 g. of aluminum isopropoxide. When the reaction is complete the isopropanol is distilled off and the residue is -'pouredinto 500 cc. of cold fiN sulfur-ic acid; An organic layercomprising 1 -heptne=5 01 appears and is separated. The aqueous layeris extracted several tir'nes-'withether-to recover the l heptene-5ol dissolved "therein; The ether eal extracts are-added to the1-heptene-5 oland the mixture is washed "with dilute sodium bicar bonate solution and Water until the -washings ate neutral. The ether solution is dried with anhydrous magnesium sulfate, the ether evaporated and the residual ..1-heptene 5-ol' purifiedibydisetillation. It boils at 9394 C. at a pressureof. about '73 mm. of mercury. h

A mixture of 79.1'g.'of'1 heptene;5-o1, 0.5 g; of diphenyl'amine, 10cc. ofglacial aceti'c acid'and. 500. of distilledxwater is treated with 113g. of an;- hydrous hydrogen bromide. gas. Theimixtureisf allowed to standlat room temperature foraboutf 2.4.hours and is then heated forabout onehali? hour and cooled. The mixture separates into-two; layers, the upper organic layer containing"2,5'-di-f bromo heptane. The organic layer isseparate'd". and the aqueous layer is heated for about.30"inin'-. utes and cooled andan' additional amounto'f '1,'5' dibromo-heptane which separate as an organic layer is recovered-and added to the 1,5-dibromoheptane already separated. The 1,5-dibromoheptane is washed with water and sodium bicarbonate solution and dried over anhydrous potassium carbonate. It is purifiedby distillation. 1,5- dibro-mo-heptane boils at-88 C. at a pressure of about 3 mm. of mercury.

To a cool solution of sodiomalonic esteripr'epared by reacting'25.2 g. of sodium in 410 cc. of ethanol and adding. 206-. g.: of .malonic-esten. are added 141. g. of 2,5-dibromoeheptane. The mix-.- ture is stirred for about l'hour and is then reffuxed with stirring for about 2 hours, and allowed to cool. Most of the alcoholis distilled off and to the residue is added lliter of water. 1,1dicarbethoxy-Z-methyl 5 ethylcyclopentane appears as an oily layer. The oily layer is separated and the aqueous layer extracted several times with ether to recover any 1,1-dicarbethoxy 2emethy1- 5-ethylcyclopentanedissolved therein. The ether extracts are combined-.withthe 'diester. already ree covered, and the mixture is driedover magnesium sulfate. The ether is 'evaporatedoff andtheresidue. comprising 1,1-dicarbethoxy 2 methyl-5 ethylcyclopentane is purified bydistillation. It boils-at-88-91 C. at a-pressure of0.2 mm; of mere cury.

17 g. of 1,1-dicarbethoxy-2-methyl-5-ethylcyclopentane are added to a solution of 4.8 g. of sodium in '70 cc. of absolute ethanol. 6 g. of urea are added and the mixture is refluxed for about 8 hours. The ethanol is removed by distillation and the residue which contains spiro(2-methyl -ethylcyclopentane-l,5'-barbituric acid) a its sodium salt is dissolved in water, and the solution acidified with hydrochloric acid. Spiro (Z-methyl- 5-ethylcyclopentane-1,5'barbituric acid) precipitates and is filtered ofi. The precipitate is washed with water and purified by repeated crystallization from dilute ethanol. Spiro(2-methyl-5- ethylcyclopentane-1,5'-barbituric acid) is represented by the following formula Spiro(2-methy1-5-ethylcyclopentane 1,5'barbituric acid) thus prepared melted at about 180.5- 181.5 C. Analysis showed the presence of 12.32 percent nitrogen as compared with the calculated value of 12.49 percent nitrogen.

EXANIPLE 9 The sodium salt of spiro(2-methyl-5ethylcyclopentane-l,5' barbituric acid) i prepared by the procedure described in Examples 2 and 4. The sodium salt is represented by the formula We claim as our invention:

1. A member of the group consisting of the spiro-barbituric acids and salts thereof represented by the formula in which R is a member of the group consisting of hydrogen and methyl, and R1 and R2 are members of the group consisting of methyl and ethyl; and R is hydrogen when both R1 and R2 are ethyl; and R is methyl when both R1 and R2 are methyl; and X is a member of the group consisting of hydrogen and alkali metals.

2. A member of the group consisting of spiro- (2,5 diethylcyclopentar 1,5 barbituric acid) represented by the formula and its alkali metal salts.

3. A member of the group consisting of spiro- (Z-methyl 5 ethylcyclopentane-1,5'-barbituric acid) represented by the formula OH; oH,- g o 0NE o0 OHPG (JO-N and its alkali metal salts.

4. The sodium salt of spiro(2,5-diethylcyclopentane-1,5-barbituric acid) represented by the formula 2H5 Na 2H5 7. Spiro(2,5 diethylcyclopentane 1,5 -barbituric acid) represented by the formula 03H; CBrH WILBUR J. DORAN. EARLE M. VAN HEYNINGEN.

No references cited 

1. A MEMBER OF THE GROUP CONSISTING OF THE SPIRO-BARBITURIC ACIDS AND SALTS THEREOF REPRESENTED BY THE FORMULA IN WHICH R IS A MEMBER OF THE GROUP CONSISTING OF HYDROGEN AND METHYL, AND R1 AND R2 ARE MEMBERS OF THE GROUP CONSISTING OF METHYL AND ETHYL; AND R IS HYDROGEN WHEN BOTH R1 AND R2 ARE ETHYL; AND R IS METHYL WHEN BOTH R1 AND R2 ARE METHYL; AND X IS A MEMBER OF THE GROUP CONSISTING OF HYDROGEN AND ALKALI METALS. 